Radar studies of bird migration in Bulgaria

Radar installed horizontally and part of the observation team (photo S. Dirksen).

The radar is used at different locations, here vertically (photo S. Dirksen).

Lesser Spotted Eagle, one of the target species of the study (photo R. Smits).

Flock of migrating White Storks (photo R. Smits)

Short-toed Eagle (photo R. Smits)

Mapping and identification of migration hot spots

As part of the ECONECT Consortium under contract of the Bulgarian Ministry of Environment, Bureau Waardenburg has played an advisory role in studying bird movements using bird radar in Bulgaria.

Under the project Mapping and identification of the conservation status of Bulgarian nature habitats and species, Bureau Waardenburg has had the task to assist in radar measurements taking place throughout the entire country in the period 1 April 2011 - 31 March 2013.

Role of Bureau Waardenburg

Bureau Waardenburg was involved in the development of the methodologies for field radar surveys of migration and local movements of wintering and breeding birds in combination with visual surveys. Furthermore, we have provided the radar for the measurements and during a course 'radar ornithology' trained local birdwatchers. Later during the fieldwork, we visited the observation points to provide location-specific advice on radar measurements.

A full coverage monitoring

The consortium has put forward a comprehensive plan to monitor bird movements at 15 observation points spread throughout the country during two consecutive years. This involved daytime observations by birdwatchers, supported by radar measurements, which later also continued during the hours of darkness. In fact, this meant measurements during 24 hours a day and in all seasons of the year. This included monitoring migration in spring and autumn, with a special focus on soaring birds, such as storks, pelicans and raptors. In addition, during winter and summer local bird movements of for example geese, storks, vultures and eagles have also been mapped by radar measurements.

Expected results

The project aims to identify the most important diurnal and nocturnal migration corridors and areas of significant value for breeding and wintering birds within Bulgaria. The results will serve as a basis to develop an elaborated guidance for conservation of birds during wind farm development in Bulgaria. For instance, a specific product of the project is a GIS bird sensitivity map for windfarm development in Bulgaria. In addition, in the most critical areas early warning systems will be developed, which will regulate the work of the wind turbines.

Using radar in bird movement studies

By using a radar it is possible to make a more complete assessment of the numbers, direction and altitude of flying birds than by traditional methods only. Birds migrating at higher altitudes, which could be missed otherwise, are regularly picked up by the radar. During the night and in conditions of low visibility it is practically impossible to quantify bird movements without a radar. Therefore, we strongly recommend to use a radar in bird movement studies, especially when details on flight altitude and flight routes are needed for impact assessments.